Update to 4.1.0.24 was available on my 2 phones by Settings/Updates/Search for updates and the usual confirmations as it is always.
Download abt. 70 MB, confirm installation, enter access code a few times and at the end the SIM PIN. Result: both phones working without any problems, all data and settings still present.
Thank you Jolla!
edit: my 2 phones are set to “early access” in the Jolla account.
A 3rd phone in my family, that is not set to “early access” does not see the both updates to 4.1.0.23 and -24.