How can I set the default match detection?

[wrohdewald]

Since I have several subdomains (I believe you say "host"), I want to change the default match detection from standard to host, or I would have to manually edit quite a few entries (imported from keepassxc).

The "help" link goes to bitwarden which allows to define the default in the user settings. I do not see this in vaultwarden.

https://bitwarden.com/help/uri-match-detection/

Is there some config file I can edit?

[BlackDex]

Not sure where you are looking then, since Vaultwarden only provides a slightly customized web-vault.

All should be the same and workable as described in that manual.

[stefan0xC]

Here's the relevant part of the documentation:

Bitwarden browser extensions and mobile apps allow you to select a Default match detection behavior from the options listed next by navigating to Settings → Autofill → Default URI match detection. You can override the globally-set detection on an item-by-item basis in all Bitwarden apps.

Base domain matching is the default option.