I have prepared a patch for chromium addressing bugs 965960 and 967124
Bug 965960 (crash on 32-bit) was caused by lack of support in the sandbox for the 64-bit time syscalls that have recently been added to Linux/glibc. I added __NR_clock_gettime64, __NR_clock_nanosleep_time64 and __NR_utimensat_time64 to the syscall whitelist. I also added __NR_clock_gettime64, __NR_clock_nanosleep_time64 to the code that filters the "clock" parameter for the __NR_clock_gettime and __NR_clock_nanosleep syscalls. After doing this the browser seemed to be usable on both Debian sid i386 and raspbian bullseye. These changes are in the patch debian/patches/allow-time64-syscalls.patch Regarding bug 967124 I started by replacing all references to "/usr/bin/python" and "env python" (mostly shebangs) with the versioned equivilents using sed. These changes are in the patch debian/patches/use-explicit-python2-sed.patch. I then changed the build-dependency from python to python2 and tried a build. This build failed with an error about being unable to find python. Some digging tracked it down to a reference to unversioned python in "gn", which I patched. This change is in debian/patches/use-explicit-python2-gn.patch . The build was then successful. I have uploaded the fixes to Raspbian bullseye. A debdiff can be found at https://debdiffs.raspbian.org/main/c/chromium/chromium_83.0.4103.116-3+rpi1.debdiff I may or may not NMU this in Debian later.