I didn’t go to my estranged father’s funeral and I don’t regret it.
I didn’t respond to a deathbed request to see him either. My only regret there is that I even entertained the notion of listening to what the go-between said.
It boils down to why you were estranged I think, and perhaps also whether you ever made a decent effort to see if things might have changed.
By dad hit my mum, cheated on her, gaslighted her about the cheating, went bankrupt (whilst hiding assets) to avoid paying child maintenance, made me and my mum homeless in the process and spread malicious lies about my mum, including to his new family. He dropped out of my life when I was eight.
In my thirties I had some contact to see if anything had changed. He was still utterly selfish. Said awful things about my mum, was repeatedly cheating on his second wife, lied to my face about things I had previously witnessed.
So I slammed that door hard. Because people like that only use and hurt others.
So if your dad was anything similar, don’t go.