Not sure if this is new in 14, but you used to have to select an app first, then select the contact in that app. Now apps can present the contacts to the share menu directly so no double tap. Funnily enough, Google Chat was the last app on my phone to support this feature.
Pretty sure there’s not a per-domain setting for that. If you have HTTPS-Only Mode turned on in the settings it will always try to use HTTPS first and present a warning before switching to HTTP.
If you want to continue using HTTPS you can setup your own CA certificate to sign certificates for your .LAN domain names. All you need to do then is add the CA certificate to your trusted certificates in Firefox and the signed certificate to the device hosting the HTTPS service.
EDIT: TIL there an exclusion feature. Neat. I didn’t see this on Firefox for Android though. https://support.mozilla.org/en-US/kb/https-only-prefs