Ok, so here is my diary.
Background: Third country national. Worked in CH from ‘05 to ‘09 (35 months) on a B permit. Returned in 2012. Kids (under 18 at the time of application) were naturalised first (2018 and 2019) because of their ages (some years counting double, as you know). They were under the old law, so I’d been through some of this before with them but the sequence and details changed a bit, especially as they did it in our former commune.
My first steps: need to apply for C permit (because of the new law).
2019-09 Pass FIDE exam in French.
2019-11 Request “early” C permit (by then I’d lived a total of 10 years Switzerland, so I probably could have done it via the normal process of requesting a C permit, but since I needed the FIDE certificate anyway, I went via the early / “well integrated” process). Could have done these steps earlier.
2020-02 Received C permit
2020-03
Cleverly, I request an apostilled birth certificate now because I know I will need it (this comes back up).
Formal process, ordinary naturalisation:
2020-03-09 Naturalisation request submitted
2020-11 Etat Civil registry asks for apostilled copies of birth certificates for myself and my wife (who is not included in the application) and our marriage certificate. First apostilled birth certificate will be too old (more than 6 months) when the other two documents arrive so I request a new one of those also.
2020-11-02 Application formally acknowledged by ServPop, request for information (copies of ID, contact info., other information), payment of CHF 450.-
2020-12-14 Part 1 completed by Serv Pop, dossier sent to commune
2021-07-05 Dossier acknowledged by commune (thanks for the delay Covid); study materials sent
2021-11-25 Naturalisation interview and knowledge test on same day (experimental measure: I was asked in the interview what I thought about that innovation. I told them I liked it as it was quicker that way). Passed the knowledge test with full marks (after hours of practice using an online app: SwissMe). Was told that the interview had gone well.
2021-11-29 Municipality approval
2021-11-30 Avis de cloture (notification of closure) from the Commune - free to relocate in CH
2022-02-14 Preavis favorable from commune
2022-02-14 Letter from Etat Civil Registry that my name on my (second) apostilled birth certificate doesn’t match some other documents, so they will go ahead and register me with that name unless I ask to change it now. They explain that the birth certificate is the definitive document for registration in the Etat Civil (I checked the law, they are right, unless I’d formally changed my name of course).
Unnecessary details: a letter in my name has an accent in French, and my home country is not familiar with accents, so they (randomly) put another type of accent on that letter in the second apostilled birth certificate (in spite of having done it correctly in the first one, and not having any accent on my passport or original hand written birth certificate from the 1970s - basically the worst mistake they could have made without adding or dropping a letter). In the interest of time I tell the Etat Civil Registry to go ahead with the error. I will have to fix that later by changing my name legally in Switzerland to the version with the right accent.
2022-03-15 ServPop send letter saying positive pre-advice has been sent to VD Council of State and then after their approval the file will be sent to SEM (now that the Etat Civil Registry have confirmed the completion of the registration). Told process could take 4 to 7 months (not explicit which process they referred to; I think it is the
SEM process only that they meant).
2022-06-15 Received SEM bill for CHF 100. Wait anxiously all summer, wondering if my application for an early C permit would make the federal review go faster (since they had to check my background for that also, just 18 months before). It didn’t
2022-07 Change communes (and inform Serv Pop)
2022-11-02 Call Serv Pop to check on process before traveling for first post-COVID long foreign vacation (don't want to miss the response deadline for the golden letter!). Told I have received approval from SEM

and thay are just doing the final checks. As there is no space left in the ceremonies for 2022, I will be invited for the naturalisation ceremony in 2023, probably Q1

. I beg for space in December, and he laughs and politely say no, but the time will come soon.
2023-01-18 (Off-screen activity) Golden letter / Invitation to the naturalisation ceremony is
sent (but
not received due to postal issue)
2023-01-25 Letter
referring to the golden letter is received. It clarifies some information that was on the missing letter (I am very confused and start checking my reycling to see if I have thrown away the golden letter by mistake)
2023-01-26 I call Serv Pop and the lady says I am not the only one who received the second letter but not the first. They will send a new letter out today (not sure if I am getting a new letter because I called or if it was already planned: the cynic in me says this is a final test of French reading comprehension and speaking ability)
2023-01-28 After two days of anxiety (plus car drama), I receive the golden letter.

The deadline to reply whether I will attend the ceremony on 22 February is next Wednesday, 1 February. I waited so late before checking the mailbox (didn’t want to go down too early and get disappointed that the postman had not yet passed) that I have missed the closing time for the local post office, so I drive a few km to an open post office and post my signed reply slip by registered mail (no messing around with such a tight deadline).
For those of you in Vaud, remember that you have to send back the slip to confirm that you will attend the ceremony so they save your space. Otherwise you get pushed to the next one (or eventually they consider you have abandoned the application). And you have to hand in your residence permit at the start of the ceremony
1'055 days since I submitted the files (thanks Covid for adding about a year)
So in 3.5 weeks I will take my citizenship oath and become Swiss!!!