In the last sslh package there was changed name of parameter ssl to tls and also something else as plain rename of ssl to tls in /etc/config/sslh and /etc/init.d/sslh does not help. This is probably request to fix to upstream but I don’t know how to send it to upstream. Issue occured after recent update in HBT branch.
Lookup the upstream package table https://openwrt.org/packages/table/start, type in the package name and the filtered result provides links to the source and bug reports.
The issue seems been fixed in upstream’s Master branch sslh: use tls option instead of deprecated ssl · openwrt/packages@46c253d · GitHub