From version 21.0.1-ucs1 on the keycloak app requires a CPU that supports the microarchitecture level x86-64-v2.
Please check that your CPU supports x86-64-v2 before installing or updating the keycloak app.
One way to check is the following script:
#!/bin/sh -eu
flags=$(cat /proc/cpuinfo | grep flags | head -n 1 | cut -d: -f2)
v2='awk "/cx16/&&/lahf/&&/popcnt/&&/sse4_1/&&/sse4_2/&&/ssse3/ {found=1} END {exit !found}"'
v3='awk "/avx/&&/avx2/&&/bmi1/&&/bmi2/&&/f16c/&&/fma/&&/abm/&&/movbe/&&/xsave/ {found=1} END {exit !found}"'
v4='awk "/avx512f/&&/avx512bw/&&/avx512cd/&&/avx512dq/&&/avx512vl/ {found=1} END {exit !found}"'
echo "$flags" | eval $v2 || exit 2 && echo "CPU supports x86-64-v2"
echo "$flags" | eval $v3 || exit 3 && echo "CPU supports x86-64-v3"
echo "$flags" | eval $v4 || exit 4 && echo "CPU supports x86-64-v4"