I've installed Media Wiki 1.35.2 from Debian-backports, and I'm using SQLite as database engine. When I edit a page with the Visual Editor, the browser waits for nearly 30 seconds on saving and then reports an error. In the debug log I see the requests for /rest.php misses the header PROMISE-NON-WRITE-API-ACTION: true.

Start request GET /rest.php/ap-1/v3/page/html/SEPA/857?redirect=false&stash=true
IP: fe80::1
HTTP HEADERS:
CONNECTION: close
CONTENT-LENGTH: 0
X-REQUEST-ID: e29da0b8f35d45af55529c76
USER-AGENT: VisualEditor-MediaWiki/1.35.2
HOST: ap-1
CONTENT-TYPE: 
(end headers)

The problem is the missing package php-curl. If it's installed it works, if it's missing it fails.
In MultiHttpClient.php:runMulti() is a switch for w/o curl and runMultiHttp doesn't pass the header (esp. PROMISE-NON-WRITE-API-ACTION: true) to the server.