Internet connection needed for home shed.

As a cheap option, that is absolutely something you could do. Yes it is as simple as plugging one port into the modem and the other into the laptop.

Here is a link to a 30 metre cable off amazon £16 : https://www.amazon.co.uk/Mr-Tronic-Ethernet-Network-Meters-Black/dp/B07V43FY55?th=1

I specifically went with the 30 metre cable, because its better to have a couple of metres too much than a metre too short.

I would strongly advise against this.

The cable I suggested is £16. The cheapest crimper with Rj45 plugs is 20. You say crimping is not hard but I always found it a pain in the ass. If there was any doubt as to whether you have done it right you would really need a connection tester, which is another £8. Thats £28 before you have bought the actual cable. And once you have done the crimping, you now have 2 tools the OP may never use again.

So yes, the OP could spend an afternoon with the help of youtube learning a skill he may never need again, and buy 2 tools he may never use again. Or he could just buy the cable and drill a slightly bigger hole. Though he never mentioned drilling a hole. If it's going to be on an ad hoc basis, he could just feed it through a window.

An alternative solution would be a wifi extender, like this one:

https://www.amazon.co.uk/TP-Link-Extender-Broadband-Ethernet-RE330/dp/B0929WHLPP/ref%3Dsr_1_3?crid=3RVAP8RYLW53E&dib=eyJ2IjoiMSJ9.Ctbjhdd2KVwlnhLtSqKgpyDKolWTO-9YYFU82q2rTxvxKBx_jUogW1KwoRzV5LwSmCMsWCjy4SC6mbILfe4mdJIy78PV7sQ_UoVCcu7iDQq55pLLNb8WE6arJRjbma6JYSGEKPvodMMlDO1nfsBJliP8_IGxxRNdqgokA92BHf9_nA_Mv6KB7ACgVXGOjtpXEnecntZwB7ddrl5fbubuKB1-fVCPEdpoK3q6FcxF6lc.PbWYRX9VGDunlIil4_efYXQ4UMsy4rge2EvzVWTT85M&dib_tag=se&keywords=tp%2Blink%2Bwifi%2Bextender&qid=1743098038&sprefix=tp%2Blink%2Caps%2C177&sr=8-3&th=1

It has a range of 150 metres so should cover the OPs need. Just configure it and plug it in nearish to the shed, and the OP can pick up the internet over wifi.