Calling Landline Numbers in Taiwan?

With Skype going away, I’m looking for a cheap alternative to call landline numbers in Taiwan from within Taiwan.

I do have a phone contract with Taiwan mobile (NT$999 monthly including home internet + 60GB 5G + unlimited 4G). However, that one only includes calling other mobile phones (120 minutes).

Recently, I foolishly assumed that calling landlines should also be included in those 120 minutes - when the next bill came, I found out that this is not the case and calling landline numbers is prohibitively expensive (for some reason…?) in my contract:

Note that those are NT$ per second!
So they charge a freaking 6NT$ per minute…

If I use my German VOIP account, I’d roughly pay 1 NT$ per minute. However, that doesn’t sound ideal as the signal would basically need to travel around the world twice…

Some banks etc. do seem to offer 0800-numbers. But those often don’t work from a mobile phone. And I don’t have a landline phone…

Any good, local alternative to calling landline numbers in Taiwan from Taiwan without breaking the bank…?

Viber out?

Do you know if they have servers in Taiwan or if they’ll also route everything to the US first or something…?

I do not. I do know they offer the service but do not know the backend.

Here are some:
This one is $0.022 a minute

This one is $0.027 a minute

Here is a local service
https://www.seed.net.tw/voip/LTY/index.php