@attilay2k I have tried a few Linux based firewall distros on Raspberry Pi over the years just out of curiosity. I have rejected all of them because the log files are useless when a large number of entries appear stamped 1 Jan 1970.
The RPi does not have a battery backed Real Time Clock so it relies on syncing with a NTP source. However, quite often log entries are made before time sync has occurred. Yes you can add a RTCmodule to a Pi but this puts the cost up further.
My preference is to use repurposed thin client terminals. There are a number of low power consumption 64-bit intel based thin client terminals that have been produced by various brands. My favourites use 1.3Ghz intel Atom 3825 dual core CPU with AES-NI.
Used prices and models vary, but I often can buy one used and upgrade it with 32GB mSATA SSD, 4GB-8GB or RAM for less cost than a comparable RPi4. The RTC, AES-NI and SSD using ZFS make it far better than a RPi.
The only downside is the number of Ethernet interfaces, usually just one. Up until 2.4.5p1 I have successfully used them in 24/7 use cases with USB Ethernet. However, with 2.5.2 and 2.6.0 now with ure driver, reliability on USB Ethernet has gone. Fortunately, for all but a few I have reconfigured them to use VLANs with a VLAN capable switch.
You may find this link useful.