LineageOS supports so many old phones, but no verified boot (bootloader relocking).
https://wiki.lineageos.org/devices/

I haven’t tried it, but I used its predecessor CyanogenMod for years without issues.

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/e/OS (a beginner-friendly derivative of LineageOS) also supports many old phones without verified boot. Some newer ones can verified-boot.
https://doc.e.foundation/devices/
The better supported ones are “official” builds while the others are “community”.
https://doc.e.foundation/devices/?channel=official

I’ve been using /e/OS community release on a Sony phone for 1.5 years. It’s okay. Most apps work with MicroG. Bootloader not lockable, but apps don’t notice.

Some bugs:

• Locked-screen camera lauch long-pressing the shutter button doesn’t work (have to unlock first)
• The arrow on the screen pointing at the side-mounted fingerprint reader points at the wrong place
• The setting about never rotating the home screen when turning the phone on its side doesn’t work, it just keeps rotating

https://www.quora.com/How-does-Murenas-custom-e-OS-compare-to-Googles-Android/answer/Harri-K-Hiltunen

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iodéOS, another LineageOS derivative, has verified boot on some devices:
https://iode.tech/iodeos-official-supported-devices/

I haven’t tried it.