Below you'll find a list of the currently available native pure-Linux (non-Android) mobile devices, listed primarily by category and secondarily in alphabetical order.

If instead you were looking for already existing/consumer smartphones that can run Linux, have a look at Can My Phone Run Linux?

Smartphones and tablet PCs

Librem 5 [$$$]

Arguably the first modern Linux smartphone.

Released: September 2019
Price: $650/$700
Specs: i.MX8 SoC (4xA53), 3/32GB, 4G modem, 3500mAh battery
OS: PureOS, postmarketOS

Necunos [$$$$]

Technically not a phone, as it contains no modem; rather a PDA. Made in Finland

Released: ?
Price: $1360/€1200
Specs: ?
OS: Debian, postmarketOS, Maemo, Nemo, LuneOS

PinePhone [$]

Source

An entry-level Linux smartphone.

Released: November 2019
Price: $149
Specs: Allwinner A64 (4xA53), 2/16-64GB, 5Mp camera, 4G modem, ~3000mAh battery
OS: postmarketOS, Debian, Ubuntu Touch, Maemo Leste, LuneOS

PineTab [$]

Source

Entry-level Linux tablet, with similar hardware configuration to the PinePhone and no modem.

Released: TBD
Price: $79
Specs: Allwinner A64 (4xA53), 2/16-64GB, 5Mp camera, ~5000mAh battery?
OS: postmarketOS, Debian, Ubuntu Touch, Maemo Leste, LuneOS

Privecall TX / Proteus Device [?]

Source

Not a smartphone (no modem) but rather a handheld/PDA aimed mostly at development and testing. Highly privacy-oriented, and very similar to Necunos (see above). Made in Helsinki, Finland. Their wiki contains some more information on the device. Very similar to the Necunos NC-1 above, so it might be very similar, if not the same device.

Released: TBD
Price: TBD
Specs: i.MX6, 1GB/8GB, Ethernet port, 3500mAh battery
OS: PriveOS, likely Debian-based

Older and discontinued devices

These devices are not available on the market anymore.

Bq E4.5/E5/E10

These devices came with Ubuntu Touch by default as an option, and are still officially supported by UBPorts.

Released: 2012/2013
OS: Ubuntu Touch

Other older and discontinued devices

2001 IBM WatchPad

You can take a look at LinuxDevices.org for an extensive archive of mostly older Linux phones, PDAs, tablets, wearables and more.