Here's the easy way:

Type 1: if your svg only has a viewbox, but no width and height, like so:

<svg viewBox="0 0 24 30">

Then you can just specify its size in css:

svg {
  height: 80px;
}

Type 2: If the svg has width and height, but doesn't have a viewport, like so:

<svg width="810" height="540">

Then you can just manually add a viewbox that's exactly the same as its width and hegith, like so:

<svg width="810" height="540" viewBox="0 0 810 540">

Then you can do the same as type 1.

Here's an easy way:

Type 1: Most SVGs have a viewbox, like so:

<svg viewBox="0 0 24 30" ...>

And you can easily control their size in css:

svg {
  height: 20px;
}

Type 2: If the svg has width and height, but doesn't have a viewport, like so:

<svg width="810" height="540">

Then you can just manually add a viewbox that's exactly the same as its width and hegith, like so:

<svg width="810" height="540" viewBox="0 0 810 540">

Then you can do the same as type 1.