This can be done with the .Fragments variable (since 0.111.0).
{{ $tocStartLevel := default 2 .Params.toc_start_level }}
{{ $tocEndLevel := default 3 .Params.toc_end_level }}
{{ $tocOrdered := false }}
{{ .Fragments.ToHTML $tocStartLevel $tocEndLevel $tocOrdered | safeHTML }}
Override the levels in front matter.
---
toc_start_level: 2
toc_end_level: 4
---