Damn... 2023? That's a surprise.
Once when my mower exhibited a similar behavior, it turned out to be the seat occupancy delay module/relay. Apparently, a relatively common failure on my 2007 ZTrak model... but that was 15 years old when it failed. I also had a seat switch housing break on my old Deere 855 CUT, which caused it to think I wasn't in the seat, but that was over 30 years old when it failed.
I've never owned a mower with a digital display, but I assume it would tell you if the brake switch didn't detect engagement, or the SCV levers weren't properly docked, or the PTO switch were still on, or it thought you were out of the seat?
There should be a simple flow chart under Troubleshooting section of your user manual, basically an idiot check list. You probably already thought of all those items (levers out, brake on, PTO off, butt in seat), but maybe worth checking. I found the bad seat delay module by following the more extensive checklists in the shop manual for my model, which I usually buy with each tractor or mower.