The steps written out:
1. Install shizuku
https://play.google.com/store/apps/details?id=moe.shizuku.privileged.api
2. Download InstallWithOptions apk
https://github.com/zacharee/InstallWithOptions/releases
3. Enable phone developer mode
https://developer.android.com/studio/debug/dev-options
4. Enable wireless debugging
5. Open Shizuku
6. Start wireless pairing
7. Grant notification perms
8. Pair in wireless debugging menu
9. Install InstallWithOptions
10. Grant always access in Shizuku to InstallWithOptions
11. Open InstallWithOptions
12. Select file, your desired apk
13. Check "Bypass Low Target SDK Block"
14. Hit install
15. Stop Shizuku (or remove Shizuku and/or InstallWithOptions)
16. Disable wireless debugging
17. Done