Recently updated to 28.0.5 from 28.0.4 and I’m experiencing this too. Logout times on my browsers (both at home and at work) seem completely arbitrary. I previously had some issues with logging out that I boiled down to “pre-loading” being enabled in Chrome.
I hadn’t had random log outs since, until I updated to 28.0.5. Just as a data point: on this laptop I’m using right now, I was logged in as of last Friday. I opened Chrome up this morning and I was still logged in. A few hours later, without even closing the browser, I went to my Nextcloud and yeah I had been logged out.
It’s frustrating enough where I’m almost considering disabling 2FA. I really don’t know how to go about diagnosing this, but it’s incredibly frustrating. I’m running this on an Ubuntu 22.04 server, and using Apache for my webserver (yes I know please don’t judge, I am old).