I would agree with NeilC's comments re the use of dubbin.
Whilst dubbin may be a good at waterproofing leather the main problems with it are that it can leave the surface of the leather very sticky/oily which attracts dust and dirt like a magnet and it is this dirt which can eventually cause the stitching to deteriorate and fail. The inclusion of someoils can over soften the leather causing the boot to lose it's shape and support over time and in extreme cases can also cause the stitching to pull through the leather. It's very rare for manufacturers to disclose the contents of this type of product so you generally have no idea what's been included and in what percentages. I don't know for definite but I would also assume that the use of dubbin could have a marked detrimental effect on the breathability of any Gore-Tex or other waterproof liner in the boot. Given those negatives dubbin is something I now actively avoid using.
Scarpa recommend the use of their own silicon based HS12 Cream or a water based wax treatment such as Aqueous Nikwax on the Montana calf leather leather used in the Terra GTX.
https://www.scarpa.co.uk/technical/boot-care/https://www.gooutdoors.co.uk/scarpa-hs12-cream-p215700MONTANA CALF LEATHERS-example-Terra
A high quality 2mm leather ideal for the entry level boots in our range. Montana leather is very supple and very lightweight which gives a soft, comfortable fit ideal for entry level boots. The leather is oiled to boost natural water resistance and to improve the cosmetic finish. Use a proofing agent from new, for best results we recommend SCARPA HS12 cream or a water based wax treatment such as Aqueous Nikwax.
Having said all that when what is probably widely regarded as one of the best boot retailers and fitters in the country offers advice on the subject of boot care I would suggest that it's probably wise to listen and take note.
https://www.whalleyoutdoor.co.uk/walking-boots-care-guide/ You can split Whalley Warm & Dry's recommended wax products in to two distinct categories. The main difference between the two types is the increased oil content in the wax for the high wear areas- Leder Gris Original has 70% wax/30% oil content whilst the Leder Gris Xtreme has 50% wax/50% oil content. Either way you can buy a tin of both types for under £10 including delivery.
Wax For Everyday All Over Use Leder Gris Original Clear (Green 80g Tin) (£4.60 upwards)
https://www.odintactical.co.uk/leder-gris-boot-waxGrangers G-Wax (£2.70 upwards)
https://www.gooutdoors.co.uk/grangers-g-wax-leather-footwear-conditioner-p342371https://www.amazon.co.uk/G-Wax-Grangers-80g/dp/B078NGW9VQ/https://www.ebay.co.uk/itm/Grangers-G-Wax-80g-Leather-Shoe-Boot-Waterproofer-Proofer-Beeswax-Polish-Dubbing/272674990800
Wax For High Wear Areas Such As Flex Point and Tongue
Leder Gris Xtreme Clear (Red 80g Tin) (£5.00 upwards)
https://www.odintactical.co.uk/leder-gris-boot-wax-clearCherry Blossom Waxed Leather Oil 100ml (£4.98 upwards)
https://www.ebay.co.uk/itm/Cherry-Blossom-Waxed-Leather-Oil-100ml/152836834522 or £3.99 collected from John Lewis if you've got a local store
https://www.johnlewis.com/cherry-blossom-waxed-leather-oil-100ml/p3497250Stafford Outdoors website is showing both Leder Gris products available for £3.96 each and the Grangers G-Wax for £2.49 all with free delivery but with very limited stock available. My only concern is that I'm sure I read somewhere that they had moved out of their premises so I'm not sure if they're still trading.
What about Carrs Leather oil the horsey fraternity use ? That can't be bad, they use it on all types of kit..
I'm pretty sure that saddles and bridles etc. don't come with Gore-Tex liners and I honestly can't see the point in trying to reinvent the wheel when someone else has already done the work for you!