Thanks for your suggestion, but NextCloud is managed on premice… i need to understand what is happening.
we can retain from the logs only the interesting information:
init rewrite engine with requested uri /fuN3
applying pattern '(.*)' to uri '/fuN3'
rewrite '/fuN3' -> 'https:///fuN3'
explicitly forcing redirect with https:///fuN3
escaping https:///fuN3 for redirect
redirect to https:///fuN3 [REDIRECT/302]