The only way to come close to a fully free web experience in 2025 is using retro tech (like an open source Zenith Z89). You would need to use BBS, because older hardware from the 1970s wouldn't work on today's internet because of Moore's Law. Swap the shugart floppy drive with a floppy8 and the device is fully open source on the hardware level. It also boots with HDOS which is proproetary, so instead use CD/M or Fuzix.
You only need a fax printer w/ phoneset so that you can route all connections via POTS phoneline instead of using digitalshit. It'll be like BBS w/ fax number as an identifier or "IP address" to the network. As long as you live in the US, it'll be free. Basically a regional network instead of global. It'll use circuit switching instead of packets – you don't need an ISP to connect. Fax doesn't use PSTN.
Every meshnet that I know of (besides GNUNet) are just overlays to the conventional web in that they require internet access. This one wouldn't.
The reason modern computer architecture wouldn't work is that while some RISC-V SBCs exist with FLOSS firmware, mainline Linux support, and blob-free firmware (like the BeagleV Ahead/Starlight, Milk-V, lowRISC/OpenTITAN, etc) these are only raspberry pi-sized boards; no desktop-sized SBCs exist currently that meet all class compliant criteria. You do have the SiFive HiFive Unmatched and Unleashed, but they come with vendor firmware of their own (namely DDR4 training). The problem with a "fully Libre'd Thinkpad" is that even if you were to scrub the firmware on the Intel chipsets, you still have the display, which is proprietary, the hard drive which is proprietary and so on. In fact, even if you had an open source hard drive (which Raptor Computing Systems is the only company that makes yhem but they're beyond most people's price range at $15,000), you'd still need Faraday protection for the hardware to prevent sidechanneling (which also applies to the Z89, which you could place in a Faraday cage and use). While it is possible to use the internet privately, however for something that's fully open source from the ground up, you'd need access to 100% blob-free hardware and the only possible route for that is retro, because there are no open source desktop SBCs currently, and whild you could slap an open 802.11 ath9k Wifi PCIe on a BEagleV Ahead w/ extra USB/HDMI ports and a ThinkPenguin 4G LTE USB Modem, thin copper heatsinks for the board, USB camera/audio, a SIM reader w/ a sysmoUSIM programmed with PySIM and Gentoo running on a resistive open source USN-based HID-compliant touch controller used for rpis (like a XPT2046) however it would be an overcomplicated setup.
So as of right now, the only full FOSS alternative on the hardware level that exists on the market today is retro tech. There's other ones you cantry too, like Mister FPGA (although you'd have to know how to set that one up) or a Checkmate display, among others.