I have 2 old Galaxies: S5 (with Android 5.0) and J1 mini (with 5.1.1) The S5 handles only 3G, whilst the mini also caters for 4G. That implies that the S5 is older, yet it does have more features (eg, fingerprint unlock). With 3G being phased-out here, makes it redundant – unless its OS could be updated, if only to 5.1. Is this possible and feasible?
S5 ended with what you have. The J1 was released later and it is a budget phone so it would have less features than the S6.
You have to find a way to root the S5 and find someone to make a rom for it. Also just because the newer supports 4G for example doesn't mean it will give the device 4G to the S5. It requires hardware more than software to support it.
@JimOz Some models of the J1 mini (2016) support 4G but not all. Samsung S5 (2014) does support 4G.
The S5 is upgradeable to Android 6 . The J1 mini LTE version (which supports 4G) is upgradeable to Android 6 also.
To use devices which don't have 5G usually takes action by your carrier. In general, they don't want 4G only devices. The 4G support is considered a backup to 5G service.
