SUMMARY
When entering accented letters in Google Documents, neither the glyph character nor the subsequent letter is displayed. Same happens in Google Presentations.
It works well in Google Mail, Google Sheets, terminal etc.
Basically, to enter an accented letter like "à" with the "English (US, alt. intl.)" layout, I first enter the glyph, like the back-quote (`), then a letter, like "a" to get an accented a (à) in the end.
It works with other browsers (Chrome, Chromium, Firefox, Vivaldi).

STEPS TO REPRODUCE
1. Setup "English (US, alt. intl.)" in KDE settings.
2. Open an empty Google Document or and empty Google Presentation
3. Click into the document area
4. Type a glyph (like the back-quote "`")
5. Type a letter (like "a")
6. Open an empty Google Sheet
7. Click in an empty cell
8. Type a glyph (like the back-quote "`")
9.  Type a letter (like "a")

OBSERVED RESULT
1. Nothing is displayed in Google Documents/Presentations
2. An accented letter ( "à") is displayed in Google Sheet

EXPECTED RESULT
2. An accented letter ( "à") is displayed in Google Documents/Presentations
2. An accented letter ( "à") is displayed in Google Sheet

SOFTWARE/OS VERSIONS
Windows: n/a
macOS:  n/a
Linux/KDE Plasma: ArchLinux (fully updated)
KDE Plasma Version: 5.27.4.1-1
KDE Frameworks Version: 5.105.0-1
Qt Version: 5.15.9+kde+r9-1

ADDITIONAL INFORMATION
Kernel Version : 6.2.12.zen1-1
Plasma Version : 5.27.4.1-1
KDE Version : 23.04.0-1
Frameworks Version : 5.105.0-1
Qt5 Version : 5.15.9+kde+r9-1
Wayland Version : 1.22.0-1
XOrg/Wayland Version : 23.1.1-1
Mesa Version : 23.0.3-1
LibVA Version : 2.18.0-1
VDPAU Version : 1.5-1