As there isn’t a timeline for Nigeria I figured I’d add ours here for those who might find it helpful.
Spouse settlement application from Nigeria (Ikeja, Lagos): non-priority
I believe the number of working days starts from when biometrics are completed.
19 August - Online submission
26th August- Biometrics and some documents submitted at TLScontact Ikeja (printed application form, passport, marriage cert, TB test, IELTS, docs checklist)
NB. We weren’t sure how long we had to send the other documents from the UK so I called UKVI and they just said to send as soon as possible but that within two weeks should be fine.
4 Sept (7wd)- Remaining documents sent to TLS Scanning Hub in London, not sure what day they were scanned but paid for the 24hr service
19 September (18wd)- Email from VISA INFO confirming application is being considered by Entry Clearance Officer (includes reminder to send docs if they’ve not been sent already)
4 November (50wd)- Email from VISA INFO asking to resend a scan of marriage cert (as it hadn't come out clearly the first time round at the TLS office) in order for application to be concluded
6 November (52wd)- Scan of certificate sent
15 November (59wd), end of week 11- TLS email saying passport is ready for collection
18 November - Passport collected
The document says the decision was made on 11 November which was day 55.
I noticed that there are some slight differences in process depending on if you have VFS or TLS in your country of application. But generally the information in this forum and a few others is very helpful and enough to guide you through the process. All the best to those still waiting.