Left #LinuxMint PC switched on overnight again with both browsers open (but fewer tabs, just #MS365 on #Edge , a terminal window and two large PDFs (a scanned copy of 1981 Handbuch für Fernmeldehandwerker (training books from DBP-Telekom) and a draft of what appears to be a University textbook (in German) about VOIP (which seems to have a better explanation about how SIP works than many English texts!).
Everything remained stable, including the Dropbox client and even the Mastodon tab left open on Firefox didn't go OOM - I suspect yesterdays crash may have been an outlier due to multiple things hammering the system (or possibly a commercial news site and the adblockers eating memory)