Can't add myself to a shared event

Steps to reproduce

1. Click on details panel of an event visible in my calendar interface. I don't own this calendar. It's visible because its owner has shared this calendar with me.
2. Try to add myself as an attendee

Expected behaviour

• I should be able to see myself in the autocomplete
• By clicking on my profile, I should be added as an attendee to the event
• A notification should be sent to other attendees to let them know I'll participate
• The event should be added to my own calendar as it happens when I accept an invitation

Actual behaviour

• I can't see myself in the autocomplete hence I can't add myself.

Calendar app

Calendar app version: (see apps admin page, e.g. 2.0.1)
2.0.4

CalDAV-clients used: (Thunderbird Lightning, DAVx5, Evolution, macOS Calendar, etc)
Using directly the Nextcloud web interface.

Client configuration

Browser: (e.g. Firefox 48)
Firefox 81.0.2

Operating system: (e.g. Arch Linux)
Mac 10.14.5

Server configuration

Operating system: (e.g. Debian 8)
don't know

Web server: (e.g. Apache, Nginx,...)
don't know

Database: (e.g. MariaDB, SQLite or PostgreSQL)
don't know

PHP version: (e.g. 7.0.3)
don't know

Nextcloud Version: (see admin page, e.g. 17.0.2)
Nextcloud 18.0.9

Updated from an older installed version or fresh install:
don't know

List of activated apps:

-- Accessibility 1.4.0
- Activity 2.11.0
- Appointments 1.7.9
- AppOrder 0.9.0
- Calendar 2.0.4
- Collaborative tags 1.8.0
- Comments 1.8.0
- Contacts 3.4.0
- Deck 1.1.2
- Deleted files 1.8.0
- External sites 3.5.0
- Federation 1.8.0
- File sharing 1.10.1
- Forms 2.0.4
- Group folders 6.0.8
- Impersonate 1.5.2
- Log Reader 2.3.0
- Mail 1.4.1
- Nextcloud announcements 1.7.0
- Notifications 2.6.0
- ONLYOFFICE 6.0.2
- Passman 2.3.6
- Password policy 1.8.0
- Photos 1.0.0
- Privacy 1.2.0
- Recommendations 0.6.0
- Right click 0.15.2
- Share by mail 1.8.0
- SSO & SAML authentication 3.1.3
- Text 2.0.0
- Theming 1.9.0
- Usage survey 1.6.0
- Versions 1.11.0
- Video player 1.7.0