I’m also able to successfully deploy but crashing on app launch - Quest (and Quest 2) with 4.26.0 ( Everything was working in Preview 5/6/7) - It seems like only a few people are affected.
Before launching onto device bring up Window -> Developer Tools -> Device Output Log - and select your Quest (Easier to see the callstack here than digging in saved/logs/ on device)
Are you seeing this as first ‘backtrace’ in device output log?
#00 pc 05dc65e0 /data/app/com.YourCompany.FouTwoSix-0VUUJ4peETxbWVN9b9xarQ==/lib/arm/libUE4.so (TRefCountPtr<FRHITexture2D>operator=(FRHITexture2D*)+40)