Look into AntiX and/or MX-Linux. They both use the same toolset, are Debian-based, while AntiX is more 'spartan', and MX more full desktop. Both can be remastered into oblivion with their delivered tools, and installed in all sorts of ways, including running from RAM.

Running as full XFCE Desktop with FF, occassional updates except kernel, all in RAM, with quick logout and telinit 1 as root from console, then back to telinit 5(with autologin back into X):

$ uptime 09:44:35 up 160 days, 46 min, 3 users, load average: 0.02, 0.08, 0.31

Most hassle-free Linux-distro I've ever had, while being compact, but fully usable for my needs. There may be others, but I'm tired of trying.

Edit: Obviously not running with this kernel-parameter or watchdog, because I don't see panics here. But could be easily integrated, because Debian. OFC you'd need to have a remastered and prepared(to your needs) boot-device available after a reboot, while running from RAM. Could even be an USB-keychain. Anyways, they have all the tools to do this within a few clicks from X and a few function key-presses and menu choices during first boot.

Works for me, YMMV.

https://antixlinux.com/

https://mxlinux.org/