Of those you mentioned, I'd avoid the iPhone because of the piss small battery, dated design with small screen. Ignore idiots who say iPhones are more efficient than Android. It doesn't change the fact that it has a piss small battery that won't last long per charge or for total service lifetime. You will already fail two of your own criteria for going with this.
I'd also avoid the S10 because in Australia you will probably get the Exynos version which is known to overheat and is inferior to the Snapdragon version (SD855)
The K30 Pro is guaranteed to come with an SD865 and has a completely uninterrupted screen. It also has the biggest battery of the lot (4700 vs 3400 vs 1821)
I suggest the K30 pro as it has the HARDWARE that will last the longest and as such will provide the most MATERIAL benefit to your usage in the long term. Focus on how the traits of the device has an ACTUAL impact on how you use it.
Tiny battery that forces you to charge more often than you'd like? That fucking sucks. Avoid that from the get go.
Small battery deteriorating quickly through increased charge cycles thus forcing you to spend to replace it to compensate for this shortcoming? Fuck that. Why get a something that YOU will have to compensate for?
Small internal storage that forces you to consume data for slower access to cloud storage? That fucking sucks. Avoid that from the get go.
Remember to think about yourself. There are many people out there who might tell you that they are fine with certain shortcomings, or how it is "good enough" for them. Your are not them.
And when someone tries to sell you on something, remember to check if the said 'feature' actually has any impact on how you use your device.
Remember to satisfy the objectives that you have laid out in the first place. Else you will make a bad decision that will leave you wanting until it is time to spend on yet another phone.