"Fixing" the URL encoding in the HTML source would be the preferred solution, as mentioned in comments (from e%CC%81 to %C3%A9). (Or even "normalising" the filename, so URL-encoding is not an issue.)
However, if that is not an option then you could perhaps do a search/replace in .htaccess.
For example, near the top of the root .htaccess file:
# Replace "e%CC%81" with "%C3%A9"
RewriteCond %{THE_REQUEST} ^GET\s/(.*)e%CC%81([^\s]*)
RewriteRule ^path/ %1\%C3\%A9%2 [NE,L]
Include a /path/ in the RewriteRule pattern (as above) to limit the number of URLs tested.
We match (and capture) the requested URL in the preceding condition against THE_REQUEST server variable, which preserves the URL-encoded URL that was actually requested.
The literal % in the substitution string should be backslash-escaped to avoid potentially being interpreted as a backreference (although since they are not followed by a digit, that should be OK).
Chrome shows Akzeptanz_GoA3+_Vorschaubild_Symbolbild_pexels-jéshoots-253647.jpg in the address bar though. When I change it in the src attribute it stays like that and loads
Chrome will often show the more friendly URL-decoded URL in the address bar, even if the underlying request is URL-encoded.
When you change it in the src attribute (to the URL-decoded version I assume) then the browser automatically "fixes" it and URL-encodes the URL in the HTTP request (you can examine the Network traffic in the browser dev tools).
éin UTF-8, URL-encoded, would result in%C3%A9. In your URL however you have a "standard"e, followed by%CC%81, and the latter is the encoding of the COMBINING ACUTE ACCENT./path/Akzeptanz_GoA3+_Vorschaubild_Symbolbild_pexels-j%C3%A9shoots-253647.jpg?Akzeptanz_GoA3+_Vorschaubild_Symbolbild_pexels-jéshoots-253647.jpgin the address bar though. When I change it in the src attribute it stays like that and loads