Starlink Brazil: custom domains time out on 216.198.79.1; alternate Vercel IPs work

Hello Vercel team,

Our production custom domains time out through Starlink in Brazil: https://realidadeoriginal.com.br/pt/a-teoria

Uma investigação em construção

A Teoria da Realidade Original (TRO) é uma proposta de investigação dedicada à construção de uma estrutura conceitual capaz de descrever a realidade a partir de princípios fundamentais comuns aos mais diversos fenômenos.

https://originalrealitytheory.com/en/the-theory

Project: realidade-original (Hobby). Both domains resolve to 216.198.79.1 and show Valid Configuration. The latest production deployment succeeded. DNS providers: Registro.br (PT) and HostGator (EN).

Tests performed:

Normal HTTPS connections to both domains time out over Starlink.
Both sites work on a phone using cellular data, but fail on the same phone over Starlink Wi-Fi, even after restarting the router.
Local DNS and 1.1.1.1 return the same A record: 216.198.79.1.
Temporary curl --resolve overrides to 64.29.17.130 and 76.76.21.21 successfully served the current production PT/EN pages from the affected Windows computer, with normal TLS validation (no -k).
No DNS, hosts-file, firewall or project configuration changes were made.

Example successful diagnostic request: curl.exe -I --connect-timeout 5 --max-time 10 --resolve realidadeoriginal.com.br:443:64.29.17.130 https://realidadeoriginal.com.br/pt/a-teoria

This suggests a reachability problem on the path to the assigned IP; these tests do not identify which network is responsible.

Could Vercel investigate 216.198.79.1 reachability from Starlink Brazil? Is 76.76.21.21 officially supported as an alternative A record for THESE existing domains/project, including continued domain verification and automatic TLS renewal? If not, what supported remedy is available? We have retained the assigned A record pending confirmation.

The Vercel support assistant suggested a network support case, but the form directed our Hobby account to this community. Please let us know what additional diagnostics would help. Thank you.

Update: Starlink support has replied. They said they cannot investigate further on their side at this stage and advised us to contact Vercel to review possible provider-side configuration or routing issues. This does not establish which network is responsible, and we do not have a confirmed resolution.

Starlink provided this geofeed for your reference: https://geoip.starlinkisp.net/feed.csv

They also suggested sharing the current public IP of the affected Starlink connection. We have not yet confirmed that address, so it is not included here. Please let us know how to provide it privately if needed.

Could Vercel review reachability to 216.198.79.1 from Starlink and advise on a supported remedy? Our earlier tests showed that temporary overrides to alternate Vercel IPs worked with normal TLS validation. We have kept the assigned DNS record unchanged pending guidance. Please also confirm whether an alternate A record is officially supported for these existing domains, including domain verification and TLS renewal.