Stupid, but I'd just lap it. Would give me the difference and worked well enough for the rare occasion I actually needed a stopwatch.
Also the Google sign in trick only works if you're signed into Google. I used to put lineage on my old phones and now GrapheneOS. I stopped doing the stopwatch thing long ago however.
Apologies for the YouTube link, but it's the only source I can find referencing it at the moment
https://youtu.be/MVXMcrRANC8
https://archive.org/details/kdewin4