I notice that in Ascii with both the stock kernel and the one from
backports (4.17.0-0.bpo.1-amd64) some applications cannot run. For
example the web browser Brave fails with this message:

[9394:9394:1015/111632.363017:FATAL:zygote_host_impl_linux.cc(116)]
No usable sandbox! Update your kernel or see
https://chromium.googlesource.com/chromium/src/+/master/docs/linux_suid_sandbox_development.md
for more information on developing with the SUID sandbox. If you want to
live dangerously and need an immediate workaround, you can try using
--no-sandbox.
Trace/breakpoint trap

This is not an issue in Linux Mint. Perhaps it is a problem upstream in
Debian?

/Lars