froi05 said:

Anyone can tell the M.2 tech specs of Aspire TC-780-UR15? Compatible M.2 drives? Is it only SATA or NVMe can work? Thank you in advance

This is the type PCIe Gen.3 M.2 SSD that is recommended for your TC-780, this is a 512GB type M.2 and what Acer OEM M.2 fits to your desktop its a; "LITE-ON SSD NAND 512GB CV1- 8B512 LF+HF - Acer part #: KN.5120L.005 and its a PCIe Gen.3 SSD. The TC-780 motherboards "NGFFM1 M.2 SSD connector is at number (9)" see caption below.

Note: you can put a higher capacity PCIe Gen.3 M.2 SSD type drive from other manufacturers also e.g. a type 1TB or 2TB or 4TB if its formatted in GPT/UEFI format which your TC-780 uses as a boot drive but, a higher capacity than 2TB PCIe Gen.3 SSD can't be used as a "Slave Drive" in Win-10 if its formatted in MBR/legacy format and not formatted in GPT/UEFI format.

PCIe Gen.3 SSD type suitable for the TC-780

TC-780 motherboard NGFFM1 M.2 SSD connector is at number (9) 

Description of all motherboard connections and components